Lubricant composition for highly stressed gears



United States Patent 3,451,930 LUBRICANT COMPOSITION FOR HIGHLY STRESSEDGEARS George A. Mead, Scotch Plains, N.J., assignor to Esso Research andEngineering Compan a corporation of Delaware No Drawing. Filed Sept. 16,1966, Ser. No. 579,833 Int. Cl. Cl0m 3/42 U.S. Cl. 252-32.7 4 ClaimsABSTRACT OF THE DISCLOSURE This invention concerns an improvedlubricating oil composition which is particularly useful in mechanicalsystems, wherein the gears are under high stresses as, for example, inrear axles and in tractor transmissions. In particular the inventionconcerns a gear lubricant containing in combination an alkaline earthmetal salt of a hydrocarbon sulfonic acid, a metal salt of a dialkyldithiophosphoric acid and a chlorinated hydrocarbon.

There are many modern day mechanical systems wherein a lubricant mustserve both as a transmission fluid and as a gear lubricant. One suchsystem is what is known as a transaxle unit wherein the transmission andthe rear axle system of an automobile are combined into a singlemechanical unit located near the rear wheels of the automobile. Anothersuch system is the transmission of a modern farm tractor. In suchmechanical systems the gears are placed under high stress and thusrequire a lubricant which will perform satisfactorily.

In accordance with the present invention it has been found that anunusually effective gear oil composition capable of satisfactorylubrication under conditions wherein the gears are under very highloads, e.g. 5 00,000 pounds per square inch, can be prepared byincorporating into the composition a combination of three types ofadditives. One of these is an alkaline earth metal salt of a hydrocarbonsulfonic acid having a molecular weight in the range of about 400 to900. A second component is a metal salt of a dialkyl dithiophosphoricacid and the third component is a chlorinated hydrocarbon. Each of theseadditives has been employed in the past as a component of a lubricatingcomposition. Chlorinated hydrocarbons are well known components capableof imparting extreme pressure properties to a lubricating oil. Metalsalts of dialkyl dithiophosphoric acids are known in the art asanti-wear agents and as anti-oxidants. Alkaline earth metal salts ofhydrocarbon sulfonic acids have been employed in the art primarily asdispersants. It has now been surprisingly found that these three typesof additives in combination exert a synergistic improvement inloadcarrying capacity.

The alkaline earth metal salts employed in this invention are the metalsalts of hydrocarbon sulfonic acids wherein the acids have molecularweights in the range of about 400 to 900. The alkaline earth metal saltsinclude those of calcium, strontium and barium. Sulfonic acids fromwhich the salts are prepared are classified generally as eitherpetroleum sulfonic acids or synthetic sulfonic acids. Petroleum sulfonicacids are produced by treating petroleum fractions, includinglubricating oil distillate fractions, the socalled white oildistillates, or other petroleum fractions such as petrolatum, withsuitable sulfonating agents including sulfur trioxide, concentratedsulfuric acid and fuming sulfuric acid. Synthetic sulfonic acids areprepared by treating relatively pure synthetic hydrocarbons in the samemanner. Usually the synthetic hydrocarbons are alkylated aromatichydrocarbons such as the products of alkylation of benzene, toluene,xylene or naphthalene. Typically benzene is alkylated with a polymer ofpropylene or butylene, e.g. butylene trimer, to form a C alkyl benzenewhich is then sulfonated as above-described. The natural or syntheticsulfonic acids whose alkaline earth metal salts are used in thisinvention include alkane sulfonic acids, aromatic sulfonic acids,alkaryl sulfonic acids, and aralkyl sulfonic acids.

The term sulfonate as used herein and in the appended claims includesboth neutral sulfonates, i.e. those wherein the sulfonic acids have beenneutralized with an equal mole equivalent of metal base, and highalkalinity sulfonates wherein additional metal base in excess of thatrequired for simple neutralization has been reacted with the sulfonicacids to form an alkaline product which is then normally blown with anacidic gas such as CO Overbased or high alkalinity sulfonates can havebase numbers of from 30 to as much as 350. Base number is defined innumerical terms equivalent to milligrams of KOH per gram of thematerial. It is preferred to employ in the present invention an alkalineearth metal sulfonate having a total base number of at least 60 and morepreferably one having a total base number of from about 200 to 350 inorder to impart rust inhibiting properties to the composition. Specificexamples of alkaline earth metal sulfonates that can be employed in thepresent invention include a barium petroleum sulfonate of about 95 0molecular weight, calcium C alkyl benzene sulfonate (from benzenealkylated with diisobutylene), barium C alkyl benzene sulfonate (frombenzene alkylated with tetraisobutylene), calcium petroleum sulfonate ofabout 880 molecular weight, calcium salt of sulfonated bottoms from Calkyl benzene (C group from tetrapropylene) overbased to 200 basenumber, a barium salt of 560 molecular weight petroleum sulfonic acidsand the calcium salts of petroleum sulfonic acids of about 450 molecularweight overbased to a base number of about 225.

The metal salts of dialkyl dithiophosphoric acids are well known in theart. It is common practice to prepare dialkyl dithiophosphoric acids byreacting phosphorus pentasulfide with an aliphatic alcohol or a mixtureof aliphatic alcohols containing the desired range of alkyl groups in amolar ratio of approximately 4 moles of alcohol for each mole ofphosphorus pentasulfide. The acids are then neutralized with an oxide,hydroxide or carbonate of a polyvalent metal, or alternatively with areactive polyvalent metal salt. The present invention employs polyvalentmetal salts of dialkyl dithiophosphoric acids prepared from alcoholshaving in the range of from about 3 to about 12 carbon atoms. Thedialkyl dithiophosphoric acids Whose salts are used in this inventioninclude not only those made from a simple aliphatic alcohol such asispropyl, normal butyl, normal decyl, etc., but also from mixedaliphatic alcohols including the C or C alcohols obtained by reaction ofolefins With carbon monoxide and hydrogen and subsequent hydrogenationof the resultant aldehydes. Also there can be used dithiophosphoricacids obtained from such mixtures as isopropyl alcohol mixed with methylisobutyl carbinol, a combination of primary amyl alcohol and isobutanol,a combination of mixed amyl alcohols and technical lauryl alcohol, amixture of isopropyl alcohol and C OX0 alcohol, and the like. Mixedacids obtained by reaction of individual alcohols separately with P 8 caalso be employed in the preparation of the metal salts. The metalsemployed in making the salts are those of Group II of the Periodic Tableincluding zinc, cadmium, barium and magnesium. Zinc salts areparticularly preferred.

The halogenated hydrocarbons employed in the present invention arepreferably chlorinated hydrocarbons, although iodinated, fiuorinated, orbrominated hydrocar- The weight percents given are on the basis of thetotal composition. In the above combination of additives the Theinvention will be better understood when reference is made to thefollowing examples which include a preferred embodiment:

bons may also be used. The halogenated hydrocarbons 5 will have ahalogen content within the range of about Example 1 35 to 75 wt.percent, or more preferably from 40 to 70 r wt. percent. Thehydrocarbons that are halogenated will A number o gear 011 eomposltlehswere p pf o fe have carbon corrtorrts ranging from about C8 to C24 The10 as the base oil a solvent refined neutral lubricating orl halogenatedhydrocarbons are produced through the direct havlhg vlscoslty 0f 0 SUSat 100 F. The three add1- halogenatiorr of tho hydrocarbons or by otherknown two components that were employed were a chlorinated means. In thecase of chlorinated hydrocarbons it is oohstttoto not less than Po P ofthe ehtlre both ordinarily necessary only to bubble the chlorine throughb o of the three types of addltlvese the hydrocarbon in the liquid StateFor example ffi 15 mgredrent that is present 1n the least concentrationshould wax can be heated to a temperature in the range of about P t waxof 50% ChlOrHle ntent, a Zlnc dlalkyl d1 to and chlorine bubbled throughit until the thiophosphate and an overbased calcium sulfonate. Thedesired amount of chlorine has been introduced. Iodina- Chlorinated waxwas a Purchased materhfl havihg a Viscotion of hydrocarbons is taught inUS. Patent 3,184,413. shy of 200 SUS at F-, and a speclfic gravity of128 The hydrocarbons that are halogenated include aliphatic at (10-6 Pgahoh)- The overbased oalolum hydrocarbons and terpenes. Chlorinatedparaffin wax is sulfohato w a Pbrohased motenal whloh was oohooh'particularly preferred, og a paraffin wax of mo1t trate in mineral Ollof a calcium sulfonate derlved from ing point that has been chlorinatedto 40% chlorine consyhthotlo atkylotod aromatlo hydrocarbons whotelh thetent or a iffi wax of melting point that has sulfomc acid-s averagedabout 420 molecular weight. The been chlorinated to 50% chlorinecontent. Other examoohoohtrate oo'htalhod 114% ootblbth toptesohtlhg Pples include chlorinated kerosene of 42% chlorine con- Ptoxlmatoly wtPercent oalohhh sultohate and 24 to tent, chlorinated polyisobutylene of850 molecular weight 25 -l e s- The total base number w about containing47% chlorine, fiuorinated petrolatum containb mllhgtams of KOH p gramThe t y ing 55% fluorine, and iodinated polyisobutylene of 780thlophosphatewas l a putehtfeed materlal whleh molecular weightcontaining 70 wt. percent iodine. Poly- 30 slsteo of an h h oohtahhhgabout 25 P e halogenated isoparaffins may also be used, including 2 ofmineral lubricating Oil and about 75 wt. percent of mm drohloro 4oh1orornothy1 24 dirrrothy1 porttane and 5 dlalkyl dithiophosphatesderived from the treatment ot a t ifl 2 2 4 t i th 1 pontano' mixture oflsobutanol and mixed amyl alcohols with The base oil used in compoundingthe gear oils of this 2 5 followed y nehtrfihlatlen w t Zlne0X1deinvention will include any of the base oils that are con- Each ofthe gear on colhPosltlohS was Prepared by ventionally employed for thisservice and can thus vary Simple mixing of the additives with thelubricating oil widely in refinement, type and viscosity. They can bedebase. In some of the compositions only one additive was rived from avariety of crudes including paraffinic, naphemployed in othercompositions two of the additives were thenic, asphaltic or mixed baseand they can be treated employed, and in a third set of compositions allthree of by any of the conventional refining methods including hy- 40the additives were employed. The load-carrying ability or". dfogeh e g,aeiel treating extraction, In general, each of the compositions wasdetermined using the Mean the viscosity Wlll be in the range of fromabout 60 to 3500 Hertz Load Test. SUS at 1000 or o usually t the T gabout The Mean Hertz Load Test is designated as Method to 21000 b 353.synthetli l F P- may 6503.1 of Federal Test Method Standard No. 791a,dated fiig g gi 5 &3 g gg gg g 2 22 23 25 in July 27, 1964. Brieflydescribed it involves use of the addition to the combination ofadditives described above, wen-known 4'ban extreme presspre testapparatus (also other additives for their known functions includinganticalled, the Shell t' test machine) Wherem steel ball foam agents,rust inhibtors, corrosion inhibitors, demulsiheld a ow 1s Pressed agamstthree other Steel bans fiers, metal deactivators, pour point depressantsand the fixed Posmon Screw and the first is like either singly or incombination, rotated against the other balls under set conditions of Theadditive combination of the present invention will force, temperatureand speed of rotation. In this particular be employed in the gear oilcomposition withi th test the force is gradually increased until weldingoccurs. centration ranges set forth below: Then the scars on the steelballs are measured, and the Weight percent 5 mean load is calculatedfrom those measurements. concentration The ingredients in each of thecompositions tested and Broad Preferred the test results expressed asthe Mean Hertz Load, kg., Metalsuuonate 0 3A 0 5 3 are given in thefollowing Table I. The concentration or ifliiegilgggflgig 1 j ach of theadditives in the table is the actual amount Higfigelgtglgalgggtfigponsutfi 0 0 that was present, ignoring the diluent oil when such waspresent in the additive as supplied.

TABLE I Blend Composition, wt. percent Base oil .A-l A-2 B-l. 13-2 0-10-2 D E F G-l 6-2 1 tfitgtae jjjjii "rd $33 i $13 t3 Chlorinated wax 3.0 3. 0 3. 0 3. 0 3. 0 Base 11 98. 5 97. 0 99. 0 98. 0 97. 0 94. 0 96. 595. 5 94. 0 s3. 5 04. 5 Mean Hertz load, kg 20. 3 42. 5 42. 3 36. 3 32.3 32.8 26. 0 40. 7 41. s 38. 3 52. 0 47. a

l Zinc dialkyl dithiophosphates.

3 Includes oil present in additive concentrate, where applicable.

It will be noted from the test results in Table I that the addition of1.5 wt. percent of zinc dialkyl dithiophosphate to the base oil produceda significant increase in the Mean Hertz Load, i.e. from 20.3 kg. to42.5 kg. However when the amount of this additive was doubled to 3 wt.percent there was no further increase in Mean Hertz Load (Blends A-1 andA-2). It is also noted that the addition-of 1 wt. percent of theoverbased calcium sulfonate to the same base oil produced a significantincrease in Mean Hertz Load from 20.3 kg. to 36.3 kg. Here againdoubling the quantity of the additive in the base oil did not result inany further increase in Mean Hertz Load (Blends B-1 and B2). Theaddition of 3 wt. percent of chlorinated wax containing 50 wt. percentchlorine produced a significant increase in the load reading, from 20.3kg. to 32.8 kg. However, when the quantity of this additive was doubledthere was no further increase in Mean Hertz Load (Blends C-1 and C2).

Looking now at the results obtained when combinations of two of thethree ingredients were employed, it will be noted that there was noincrease in the Mean Hertz Load when 2 wt. percent of the overbasedcalcium sulfonate was added to the composition that contained 1.5 wt.percent of the zinc dialkyl dithiophosphate (Blend D) nor when 3 wt.percent of chlorinated wax was added to the blend containing 1.5 wt.percent of zinc dialkyl dithiophosphate (Blend E). While the addition of2 wt. percent of overbased calcium sulfonate to the oil composition thatcontained 3 wt. percent of chlorinated wax (Blend F) resulted in someimprovement in the load reading, i.e. from 32.8 kg. to 38.3 kg, thevalue reached was not as high as that when 1.5 wt. percent of zincdialkyl dithiophosphate was used alone, i.e. 42.5 kg. (Blend A-l).

Referring now to the compositions wherein all three of the componentswere present, it will be noted that a combination of 1.5 wt. percent ofzinc dialkyl dithiophosphate, 2 wt. percent of the overbased calciumsulcfonate and 3 wt. percent of chlorinated wax gave a Mean Hertz Loadof 52.0 kg. (G-l which is higher than would be expected by doubling theconcentration of the individual additives or by adding one of theadditives to the composition containing just one of the other additives.Similarly, one-half as much of the calcium sulfonate was employed in thecomposition containing all three components (G-Z). A load reading of47.3 kg. was obtained. Thus there was a surprising synergy in theload-carrying ability of the composition when all three of the additiveswere present.

Example 2 Additional blends were prepared employing the same base stock,the same chlorinated wax and the same zinc dialkyl dithiophosphate asdescribed in Example 1 but different metal sulfonates. One of these wasa 45 wt. percent concentrate in oil of a neutral calcium petroleumsulfonate derived from 450 molecular weight petroleum sulfonic acids.The other was a 45 volume percent concentrate of a high alkalinitybarium synthetic sulfonate derived from alkyl benzene sulfonic acids ofabout 460 molecular weight. The concentrate analyzed 14.5% barium andhad a total base number of about 59. Blends containing all threeingredients, i.e. either of the sulfonates just described along with thezinc dialkyl dithiophosphate and the chlorinated wax, were compared withother blends containing only either of the described sulfonates. TheMean Hertz Load data that were obtained and the compositions of each ofthe blends are given in the following Table II. Here again, the actualconcentration of each additive is given, ignoring the diluent oil.

Zine dialkyl dithiophosphates. 2 Includes oil from concentrates.

Example 3 A gear oil blend suitable for use in the present invention isprepared by blending together 73.3 wt. percent of the base oil describedin Example 1, 17.4 wt. percent of solvent-deasphalted, solvent-dewaxedMid-Continent residuum of about 207 SSU viscosity at 210F., 0.5 wt.percent of a pour point depressant comprising wax-alkylated naphthalene,2.0 wt. percent of a 70 wt. percent concentrate of zinc dialkyldithiophosphates in lubricating oil, said dialkyl dithiophosphates beingderived from a mixture of P 8 treated isopropyl alcohol and P 8 treatedmethylbutyl carbinol, 3.0 wt. percent of a chlorinated kerosene of 41%chlorine content and 4.0 wt. percent of an overbased calcium sulfonateconcentrate comprising 42 wt. percent of diluent oil and the balance theoverbased additive. The base number of the calcium sulfonate concentrateis 250 and the calcium sulfonate is derived from petroleum sulfonicacids of about 450 molecular weight.

Example 4 A gear oil composition was prepared by simple mixing of 74 wt.percent of the base oil described in Example 1, 17.5 wt. percent of theresiduum described in Example 3, 0.5 wt. percent of the pour pointdepressant described in Example 3, 1.0 wt. percent sorbitan monooleaterust inhibitor, 2.0 wt. percent of calcium sulfonate concentrate, 3.0wt. percent of chlorinated paraflin wax and 2.0 wt. percent of zincdialkyl dithiophosphate concentrate, those last three additives beingthose described in Example 1. The Mean Hertz Load for this compositionwas found to be 56.4 kg.

This composition was used to lubricate a farm tractor transmission thatcontained all of the usual transmission gears together with the finaldrive gears, which included a spiral bevel pinion and ring gear. Thetransmission was run with this oil composition at an oil temperature of180F. with a load that placed 450,000 to 500,000 p.s.i. contact stresson the final drive gears. Under those conditions the run lasted for morethan 2.00 hours before failure of the final drive gears, which wasconsidered to be excellent performance.

Thus the compositions of this invention are particularly suitable forlubricating transmissions having gears that are subjected to contactstresses of at least 450,000 pounds per square inch.

It is not intended that the specific examples herein presented limitthis invention in any manner.

What is claimed is: a

1. An improved lubricating oil composition capable of serving both as atransmission fluid and as a lubricant for gears subjected to highstresses, which consists essentially of a major proportion of alubricating oil base and a minor proportion of a load-carrying additivecombination of:

A an alkaline earth metal salt of a hydrocarbon sulfonic acid having amolecular weight within the range of about 400 to 900;

B. a zinc salt of a dialkyl dithiophosphoric acid wherein the alkylgroups are within the range of 3 to 12 carbon atoms; and

C. chlorinated parafiin wax having from 35 to 75 weight percentchlorine;

each of said components A, B, and C constituting 7 at least 15 weightpercent of the total of A plus B plus C; there being present in saidlubricating oil composition, based on the total composition, from about0.3 to 4 weight percent of A, from about 0.2 to 3 weight percent of B,and from about 0.5 to 10 weight percent of C; the amount of C that ispresent in said lubricating oil composition being such as to impart tosaid composition from about 0.2 to 3 weight percent of chlorine. 2.Lubricant as defined by claim 1 wherein said sulfonic acid salt has atotal base number of at least 60.

3. Lubricant as defined by claim 1 wherein said sulfonic acid salt is anoverbased calcium sulfonate of about 300 total base number.

4. Lubricant as defined by claim 1 wherein said dialkyl dithiophosphoricacid salt is the zinc salt of mixed C -C dialkyl dithiophosphoric acids.

References Cited PATRICK P. GARVIN, Primaiy Examiner.

US. Cl. X.R. 25275

